gh-131798: Add _IS_NONE to the JIT optimizer

[Wulian233]

Hello! This is my first time submitting something to JIT. I'm still learning, so there may be some mistakes. Welcome corrections!

• Issue: Better uop coverage in the JIT optimizer #131798

[Fidget-Spinner]

Thanks for contributing to the JIT, and welcome!

[Fidget-Spinner]

You can replace this whole chunk with

        b = sym_new_type(ctx, &PyBool_Type);
        REPLACE_OPCODE_IF_EVALUATES_PURE(value, b);

[Wulian233]

Thank you! Currently, I have the following code in my local environment:

    op(_IS_NONE, (value -- b)) {
        b = sym_new_type(ctx, &PyBool_Type);
        REPLACE_OPCODE_IF_EVALUATES_PURE(value, b);
    }

However, when running optimizer_generator.py, it throws the following error:

File "E:/cpython/Python/bytecodes.c", line 3519

                ^
SyntaxError: 'value' is cleared on some paths, but not all

next step, should I replace

cpython/Python/bytecodes.c

Lines 3511 to 3520 in 72006a7

	op(_IS_NONE, (value -- b)) {
	if (PyStackRef_IsNone(value)) {
	b = PyStackRef_True;
	DEAD(value);
	}
	else {
	b = PyStackRef_False;
	DECREF_INPUTS();
	}
	}

with the following?

        op(_IS_NONE, (value -- b)) {
            b = PyStackRef_IsNone(value) ? PyStackRef_True : PyStackRef_False;
            DECREF_INPUTS();
        }

I apologize if this is a basic question

[Fidget-Spinner]

Are you sure you're in the right file? You should be editing optimizer_bytecodes.c not bytecodes.c

[Wulian233]

yeah, looks this😥

[Fidget-Spinner]

That's probably a bug in the cases generator then. Let's just use your current approach for now but fixed.